This invention relates to the installation of cable such as along a series of utility poles, and, more particularly, to a cable block for temporarily supporting a section of aerial cable prior to its being lashed to a supporting strand.
In the installation of aerial cable, such as coaxial communication cable, a so-called lashing method is employed wherein the cable is secured to a supporting strand (or so-called messenger) by wrapping a fairly large gage lashing band in spiral fashion therearound. Prior to the lashing operation, the aerial cable is temporarily supported in close proximity to the strand by a plurality of cable blocks mounted on the strand, and typically spaced apart at intervals ranging from 10 to 20 feet along a given span thereof, i.e., between a pair of utility poles. The cable blocks are subsequently cumulatively pushed along each successive span of the strand by and ahead of a lashing machine. Upon reaching any given pole defining the end of a lashed cable span, the then stacked array of cable blocks are removed from the strand by a workman, and re-mounted in a spaced array along the next succeeding span of the strand. Thereafter, the lashing machine is also transferred to the other side of the then adjacent pole, and positioned on the strand in front of the first re-mounted cable block in readiness for lashing a new section of cable to the strand along that particular span. In some applications, new cable is lashed to existing cable previously lashed to the strand.
In such an aerial cable installation, it is appreciated that the cable blocks should be constructed such that they are reliably and easily mounted on the supporting strand, and readily movable therealong in the direction of movement of the lashing machine. It is also very important, however, that such a cable block incorporate means to effectively control its longitudinal movement along the supporting strand so that it moves only when and as desired.
Effective control of the cable blocks"" movement is very important as the unlashed cable supported thereby tends to exert variable and appreciable longitudinally directed forces on the blocks in the forward and rearward directions along the supporting strand. Such forces are most pronounced when forcing the cable block along the supporting strand, during the threading of a winch line over the respective pulleys of the spaced array of cable blocks, and while the free end of a new reel of cable is pulled thereby over the rollers preparatory to the lashing of that unwound reel of cable to the supporting strand. Even after a portion of a new unwound reel of cable has been temporarily supported by the spaced array of cable blocks along any given span between two utility poles, any excess length of such cable that extends between the last cable block and the ground (or supply reel on the ground) will exert a substantial longitudinal force, in the direction of the lashing machine, against that block initially and, thereafter, possibly against one or more adjacent blocks in a cumulative fashion if they are allowed to become bunched. Thus, unless a longitudinal control mechanism, such as a clutch, is incorporated in the cable blocks to prevent such displacement, they can very readily defeat the purpose intended therewith.
It is also important that the cable blocks grip the strand such that they remain in a substantially vertically oriented position at all times so as to facilitate the guiding of the cable therethrough, as well as through the lashing machine. This also minimizes any tendency of the cable blocks to become jammed on the strand while being cumulatively pushed in tandem by the lashing machine, and also minimizes the possibility that the blocks could become accidentally dislodged from the strand due to very strong gusts of wind, for example.
A prior cable block intended to provide some longitudinal movement control are disclosed in U.S. Pat. No. 3,134,575 to O. L. Walter, and, U.S. Pat. No. 4,019,715 to A. Vugrek. These cable blocks utilize spring-biased and pivotally mounted cams to effect the locking of the cable block from movement along the strand in only one particular direction, but are deficient in that they allow relatively free movement in the opposite direction. This requires the installer to position the cable blocks in a particular direction according to the direction of the forces anticipated. In addition, such mechanisms have also been found to not always provide the degree of positive locking action desired, particularly during the aforementioned winch-line pull-through of a new length of cable, or when hilly terrain is involved.
In addition to the aforementioned desired and important operating characteristics that have been urgently sought in cable blocks heretofore, there has also been a need for a cable block that could equally prevent undesired movement and allow desired movement in either direction. This would allow the cable blocks to remain in place even when subjected to oppositely directed unintentional forces, such as when on opposite sides of a utility pole.
Additionally, it has been a necessity of prior art cable blocks to place alternate cable blocks onto the supporting strand in opposite directions, as shown in U.S. Pat. No. 4,019,715, and to orient the cable blocks according to their forward and rearward operating characteristics, which are both quite burdensome for the installer. The present invention""s symmetry in operation allows successive blocks to be positioned without regard to their directions, thereby allowing the operator to install all blocks more simply from the same side of the supporting strand, or without any regard to their directions at all. This is a huge advance to the installation process.
It, therefore, is an object of the present invention to provide a new and improved cable block of simplified, rugged and reliable construction, and which can readily and reliably be mounted on a supporting strand in either direction, maintained in a substantially vertical position, and be readily adjusted so as to allow controllable longitudinal movement along the strand in either direction, relative to a given, as mounted, orientation on the strand, while being sufficiently locked against any undesired movement.
In accordance with the principles of the present invention, the above and other objects are realized with a cable block comprising a main frame member formed at its upper end with an inverted V-shaped strand engaging hanger section, at its lower end with a U-shaped pulley support section, and with a spring-biased, clutch mechanism supported on the upper hanger frame section.
Considering the clutch mechanism more specifically, it comprises a pair of jaws that are positioned so as to grasp the supporting strand and that are biased together by a spring. The jaws and spring are dimensioned and arranged so that the clamping force on the supporting strand is sufficient to hold the cable block to the supporting strand and deny longitudinal movement even during any unintentionally applied moving force exerted on the cable block, such as wind or the weight of the cable. Yet the clamping force is weak enough to provide a clutch effect that allows longitudinal movement of the block along the supporting strand by intentionally applied moving force such as that used during the usual lashing operation.
Additionally, the clamping force provides the same clutch effect in both directions so that the cable block will function equivalently regardless or the direction it faces or the side of the supporting strand from which it is attached.
The symmetrical nature, configuration and clamping action of the clutch also insures that the cable block, while being pushed along the strand, grips the latter in such a way that the block remains substantially vertically oriented at all times. This, of course, greatly minimizes the possibility of cable block jamming, or dislodgement from the strand.
It should be appreciated that the cable block embodied herein, and described in greater detail below, has universal application in that it may be suspended from any elongated member of generally circular cross-section defining a span between two spaced supports, and temporarily support a second elongated member of similar cross section in close proximity to the first until the two elongated members are permanently secured to each other along the span in a desired manner. However, for purposes of illustration, the subject invention is disclosed herein in connection with one preferred application, namely, the installation of aerial communication cable, wherein cable blocks of the type embodied herein are used to temporarily support the cable along each successive span prior to its being lashed to the supporting strand (or messenger). In that connection, further details and advantages of the invention will be appreciated with reference to the following drawings and description of the preferred embodiment thereof.